AD7873 Analog Devices, AD7873 Datasheet - Page 7

• Manufacturer Part Number: AD7873
• Description: Touch Screen Digitizer
• Manufacturer: Analog Devices

Specifications of AD7873

• Resolution (bits): 12bit
• # Chan: 6
• Sample Rate: 125kSPS
• Interface: Ser
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni 2.5V
• Adc Architecture: SAR
• Pkg Type: CSP,SOP

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
Table 5. Pin Function Descriptions
LFCSP
3, 10
11
12
13
14
15
16
1
2
4
5
6
7
8
9
Pin No.
QSOP/
TSSOP
1, 10
2
3
4
5
6
7
8
9
11
12
13
14
15
16
PENIRQ
+V
V
AUX
REF
Figure 3. LFCSP Pin Configuration
CC
1
2
3
4
Mnemonic
+V
X+
Y+
X–
Y–
GND
V
AUX
V
PENIRQ
DOUT
BUSY
DIN
CS
DCLK
BAT
REF
(Not to Scale)
CC
AD7873
TOP VIEW
PIN 1
INDICATOR
12 Y+
11 X+
10 +V
9 DCLK
Function
Power Supply Input. The +V
connected directly together.
X+ Position Input. ADC Input Channel 1.
Y+ Position Input. ADC Input Channel 2.
X– Position Input.
Y– Position Input. ADC Input Channel 3.
Analog Ground. Ground reference point for all circuitry on the AD7873. All analog input signals
and any external reference signals should be referred to this GND voltage.
Battery Monitor Input. ADC Input Channel 4.
Auxiliary Input. ADC Input Channel 5.
Reference Output for the AD7873. Alternatively, an external reference can be applied to this input.
The voltage range for the external reference is 1.0 V to +V
the AD7873. The internal 2.5 V reference is available on this pin for use external to the device. The
reference output must be buffered before it is applied elsewhere in a system. A 0.1 μF capacitor is
recommended between this pin and GND to reduce system noise effects.
Pen Interrupt. CMOS logic open-drain output (requires 10 kΩ to 100 kΩ pull-up resistor externally).
Data Out. Logic output. The conversion result from the AD7873 is provided on this output as a
serial data stream. The bits are clocked out on the falling edge of the DCLK input. This output is
high impedance when CS is high.
BUSY Output. Logic output. This output is high impedance when CS is high.
Data In. Logic Input. Data to be written to the AD7873 control register is provided on this input and
is clocked into the register on the rising edge of DCLK (see the Control Register section).
Chip Select Input. Active low logic input. This input provides the dual function of initiating
conversions on the AD7873 and enabling the serial input/output register.
External Clock Input. Logic input. DCLK provides the serial clock for accessing data from the part.
This clock input is also used as the clock source for the AD7873 conversion process.
CC
Rev. E | Page 7 of 28
CC
range for the AD7873 is from 2.2 V to 5.25 V. Both +V
Figure 4. QSOP/TSSOP Pin Configuration
+V
V
GND
AUX
BAT
X+
Y+
X–
Y–
CC
1
2
3
4
5
6
7
8
CC
(Not to Scale)
. For specified performance, it is 2.5 V on
AD7873
TOP VIEW
16
15
14
13
12
11
10
9
DCLK
CS
DIN
BUSY
DOUT
PENIRQ
+V
V
REF
CC
CC
pins should be
AD7873